According to the press release, tumors in rats more closely resemble tumors in humans than do those in mice. Previously, only mice were easily engineered with knockout genes (requires free registration), but rats are a better model of human physiology and are easier to work with. Being able to do additional research with mice and rats decreases the number of larger animals, such as primates, needed in biomedical research.
Subscribers to Nature, or people with $30, can read the full paper online, and anyone can read Nature’s article on the story for free. The UPI also covered the story (second from top in the series) in its “Stories of Modern Science.”
Update [2003-5-20 20:40:43 by rickyjames]: Also of interest on this topic is a previous SFT/Sciscoop story on knockout mice from three weeks ago on a four-gene network that controls female behavior.